Toll trunk selection



March 4, 1947. MYERS I 2,416,711

TOLL TRUNK SELECTION Filed se i. 7, 1945 s Sheets-Sheet 1 sea/trek v recurs ram-rm .neu rs FIG. I

INVENTOR V QMYERS C ATTORNEY March 4, 1947. o} MYERS 2,416,711

TOLL TRUNK SELECTION Filed Sept. 7, '1945 5 Sheets-Sheet 2 mum awcx RELAY IN l ENTOR QMYERS BY March 4, o MYERS TOLL TRUNK SELECTION Filed Sept. 7, 1945 s Sheets-Shet 5 I'll //v l/EN r09 0. M y E R5 ATTORNEY Patented Mar. 4, 1947 ;sc ar -Mye rsQ Mount Vernomassignor to I pies,-Incorporated,New

I H .flji'fYork, N. Y a corporation ofihlewYork v i i.

1 Application September 7, 1945,'S eiial No'. 614,957

" ciaims-J (c1. 179-'2'7 Bell Telephone Laborato This invention relates totelephone systems and has for its object to facilitate the completion of toll connections during busy calling periods.

Toll ofiices, ingeneral, serve to establish telephone connections between exchange areas, such connections including thoseoutgoing from a local exchange for completion through a toll oiiice in a distant exchange area, those incoming from a toll office in a distant exchange area for completion at a local exchange andthose for interconnecting two distant toll oflices;

The number of toll lines provided between two toll 'ofiices is based on the normal volume and nature of the traffic between the offices and, connumber of the remaining trunksmade accessible to incoming calls in accordancewithnthe nature;- of such calls. i i r.

These and other features of theinvention will;

j be more apparent from aconsideration ;of-;the

following description in connectionwith the accompanying drawings, in which J l A Fig. lshows a part of a; marker at atoll 'ofiice 1 for controlling the routing of incomingcalls;

Fig; 2 shows some of the trunk testing-relays 4 ofthemarker;and' Fig. .3 shows, in diagrammatic form, a connection from a callingsubscribers line to the toll ofllce and, "in detail, an overflow trunk.

sequently, during busy periods there are occasions 5: --These& figures are based on Figs. 3, 4 and -5 of when the demand for'lin'es'to certain tollofiices the above-identified 'McKim-Myers patent and is greater than thenumber of lines extending reference is made thereto for a more comprehene thereto and the completion of connections to sive description of the toll switching system to; theseoffices is delayed.- which the present invention relates.

In manual toll OfflCGS it is a simple matter for 2 Assuming thatthe subscriber at substation300, the toll "operator to explain the delay, but in associated with oflice l,'wishes to make a toll automatic switching toll ofiices, special means call,'he will dial the appropriate code and be'con-- must be provided torelieve the operators at the nectedwith the'toll operators position atgofllcecalling exchange from making repeated fruitless 3M; This operator will make a record of the de-" attempts to secure an idle line for a desired toll 25 tails of the call and, finding that the call must be connection;

In the toll switching circuits disclosed'in Pat ent No.'2,382,893, granted Aug-:14, 1945, to 'B;

McKim and. v0. Myers, connections are set up. underthe control of-registersenders and markers in responseto; the registration--01 pulses desig-- nating the-desired'groutex These gmarkers areprovided with means, responsive to theregistration of the designation, for automatically .-re n routing all incoming-calls for ;a congested T011136);

to a. special operato busy or idle condition of the trunks. Means is rs position irrespective of the also provided in the marker, to indicate when the special operator is calling, which'means disables the automatic? rerouting means and permits her to complete the caillwhen an idle trunk is available Indicating special operator, when one'of thetrunks of the congested route becomes available? 6 It has been-found that when an entire trunk group is reserved for use by the specialfoperators,

it is not possible for the operators to use the group athighestefiiciency. j j q In accordance with ,theqpresent: invention means ,isprovided in cases of traflic-congestion means'is alsoi provided-to inform the route relay is operated tocontrol the'selection' for reserving aportiom of a'trunk'group fonthe 1 exclusive use of thespecial operators.

Furthermore, means is provided effectivewhen I certain trunks are so reserved, for varyihg}.tne;$ 5

routed through the cross bar toll ofllce willselzea toll trunk line leading to that oflice where it ter-a minates-rinthe incomingtrunk circuit 302.

: The seizure of the toll trunk line causes the:v

; transmission off-a signal-to the" incoming trunknumerical digits identifying theywa ntedline to the sender-I00 where they; are registered on the sender registers. As soon as the code digits have been-registered, the -marker connector lfll is operated to-connect sender-I00 with the marker, parts of whichare shown in- Figs. 1 and:2'.,. The? code" digitsiare then transferred-to the marker registers I25; From-the marker registers, control" relays- I20 :and I2 I are; operated; after which aandtest of a trunk outgoing-to the wanted oflice.-- For example, route relay I I0 is' operated in a-cir cuit' from battery through its winding, over contacts of :contro'lrelays HI and I20; contacts .Of- 7 the register relays l25 to ground attheback coni-" tactoi-relay'llil. 7 1 With route relay. 0- operated, a .trunkbloclrv relay indicated by rectanglediifl is pperated JJOj connectthe, trunk test-relays of the marker with a stern Q ru kst fi d hr the r t w e -f 1 As described in detail in Patent 2,236,246 to G. V. King, J. B. McKim and 0. Myers, granted March 1 25, 1941, there are forty test relays of which only i 3 six are shown in Fig. 2 with each of which is associated a group start or a group end relay and a select relay. Trunk groups may include any even I number of trunks, the route relay controlling circuits for determining-which of the test relays shall As indicated in the. drawing, the trunk group,

selected by trunk block relay 230 includes ten trunks, of which six trunks are indicatedbythew rectangles OGTD to OGT9. With route relay I I operated, group start relay 200: is'operated in a circuit from ground on conductor I51, contaot13' of relay ll, contact 4 of route relay H0; contact l of relay H5, winding .ofirelay2ll0 t'o.bat-- be effective in testing'a particular trunk'group.

- and are associated with the test relays immetery. At the same time group end relay, 209 is j operated in a circuit from ground on conductor I51, contacts 3 and l of relay 5l, normally closed contact 2 ofrelay 265 contact: 3 of'relay' H0,

winding of relay zlld'and'battery. Included in each trunk circuit is a; relay as indicated inthe rectangles,- which operates when a trunk is taken for'use to mark it busy, co-nnecting ground to a path-'which-is extended by the trunk block relay, whenoperated', to a. corresponding test relayin the marker; When trunk OGTllis busy, relay l3! is'-operated;and'ground is connected to conductor 250 so that with trunk block relay 230 operated a circuit is. completed over contact I of relay 220'through' the winding of relay 2H1 to battery over' cond'uctor 26L All trunks that are busy, therefore, arein'dicated by the operation ofthe corresponding'test relays, as

soon as the trunk grou is associated therewith? A measured interval later; ground is connected to: conductor 25!] to complete a circuit for operating one of the trunk selecting relays: 220- to 229'. Assumingi,that only trunk OGTD' is busy, and therefore that relay 2H1 is the only" test relay operated, ground connected .to conductor- 250 completes a circuit that may be traced over contact 3 of relay 209, contacts 2 and 3 of relay 251]) contact 2 of testrelayfll fl', contact I of relay'Z-I I, winding: of relay 22! to battery over conductor 263. litela'yflil operatesin this-circuitjlockin'g' over its contact 4 and connecting battery from conductor 264 over its contact3' to the select magnet individual to the selected "trunk. Relay.

22 l' at its'contact 2 connects ground to' conductor 25 I to mark: the'trunk busy and initiates the furv ther' operation of the marker to operate the neces:

sary cross bar switches to connect the incoming.

trunk circuit with an outgoing. trunk 7 leading to the wanted-office;

If all of the trunks of the selected group had been busy, as indicated by the operation of test relays zmit'o 21'9; inclusive, the circuit completed by the grounding of' conductor-260 would have extended as abovei'traced'to contact 2m relay-21.3 r

and thence over contact 2 of relay 2 l I, contact- 5 of re'l'ay2ll:l vcontacts of the relays associated with" the third and fourth trunks, over contacts 2of relay 21 4 and 215 and c'ontact- 6 or relay 2H5;

over similar contacts of'the relays associatedwith the seventh and eighth trunks, contacts 2 of-relays' 2-l-8 and 2 l 9., contact 5 of relay 2 3'9" to the winding of relay 158 and'battery'. Relay I58 in turn oper- Y ates re1'ay'l-5'l and these; relays control the oper ation of the marker in testing additionaltrunk groups-"testing overflow trunks the call tdan operatori Associated'with each group of trunks is a g oup busy renysucn "as relay 355 which, is held oper or inrerouting diately following the test relays used to test the working trunks.

When an idle ;o.v,erflow trunk is found the cross bar switches, represented by switch 394, are operated extending the incoming trunk circuit 392 to the:v overflow trunk shown in Fig. 3. When the overflow trunk is seized, relay M5 is operated, in turn operating relays 3311 and 3| 4. With relay 3M operated, the simplex circuit connecting the tip and ring conductors of the trunk and the 1 windings of coil M3 is extended over co-ntact6 of relay 3M, through resistance 332' and a contact of relay 3% to ground; Relay 340 is intermittently operated under the control of overflow in terrupter 335 or reorder interrupter 333 depending 1 onthe operated or non-operated condition of relay 355; overflow trunk, groundis'supplied to the arma ture of' interrupters 333 and 335 so'that relays 337 and 338 are operated intermittently, relay 33! being operated-thirty times per minute-while relay 338 is operated-one hundred times perminute. These relays in turn supply ground to contacts of the trunk busy relays such as 'rel'ay 355. With relay 355 released" in response to an all trunks husy condition as assumed above ground from the contact of relay 331 i connected over contact 2 of relay 355 and'contact llllof relay 34l to the winding of relay 340, the circuitof relay 34!! extending over contact I of relay 34!, contact 3 of relay 330, and through resistance 33lto battery. Therefore relay 34!] operates thirty times a minute to intermittently ground the simplex circuit as a signal that all of the trunks leading to the wanted office are busy. When one or moreQof these trunks becomeidle, relay 355 reoperates and transfers the circuit of relayQilover contact I of relay 355 tothe contact of reorderrelay 338, thereby' 'op'eratingrelay 349: at a rate of one hundred t'wentyt'imes perminute" as-a reorder signal to the-calling operator.

- If a particular route becomes congested so that there isa considerable delay in completing calls there'oven'the overflow trunks individual to that route may be connected to a delay operators p'cv sition by inserting a patching cord in the jack 1 associated with the trunkand' in a jack connected to a circuit leading to the delay position, for example cord 32llmay be inserted in jacks 319" and} 32], after which calls directed to the overflow trunk of Fig. 3 will be answered by the delay op erator who can informthe-callin operator" as to.

the probable delay. The insertion of the plug of cord 326 in jack 315 closes an obvious circuit for operating relay 3 which, at contacts I and Ill opens the circuit of relay il lllto prevent-the transmission of the overflow and reorder signals to the calling operator, and at contact 9 prepares a cir cuit for operating relay 340' under the control of the delay operator to transmit an answer signali instead. =At contactl relay 3M1 connects ground i over conductor-318, contact l' of relay llt, back contact of relay I01, winding of polarized relay iras tobattery."

Whenever a call is directed. to'an v Relay H18 in turn operates relay I I6 which locks over its contact 3. With relay H6 O erated only-a limited number of trunks of the group belonging to-the route are available for use by incoming calls in general. The group start circuit previously traced to the winding of relay 200 now extends from contact 4 of route relay H0, over contact 2' In addition it may be desirable to permit the trunks used by cordless board operators at thetoll ofllce or certain groups of incoming trunks to have access to a larger portion of the trunk group. When such trunks are connected with a sender, the sender receives an indication'of the nature of the trunk and supplies ground for operating relay I05. With relay I05 operatedthe group start circuit extends from contact 4 of relay H0, over contact 2 of relay H6; front contact'of relay I05, contact 5 of relay I II) to the winding of" relay 294 and battery. Therefore, incoming trunks of these types have access to trunks OGT i to OGTQ in the group corresponding to route relay I I0. I i

In either case, if all of the trunks of the group are found busy, relay I58 is operated as'previously described, in turn operating relay l5! These relays dispose of the calls as described in the Mo- Kim-Myers patent previously identified, certain calls, for exampl those incoming from one dis-;

tant office for extension to another distant toll office. being routed automatically to the delay operators position. 4 y

When the delay operator attempts to complete a 2. In a telephone system, anautomatic' switching oflice, a plurality of; other ofilces, said automatic switching omce having incoming trunks from said other ofiices and outgoing trunks to said other ofiices in groups according to the code desig-' nations of said otheroflicesycontrol means com?" mon to said trunks, means for seizing said concall, an indication is given to the sender which" erator, while other calls have access to diiferentportions of the group in accordance with their class.

n will be apparent thatth'e'numbers of trunks shown as inc uded in the total and fractional groups are illustrative only and that the various route relays will be wired to provide trunk groups and subgroups of the size demanded bythe traffic over the associated routes.

What is claimed is: I V t 1. In atelephone system, an automatic switching office, a plurality of other offices, said automatic switching o-ffice having incoming trunks from said other offlces and outgoing trunks to said other ofilces in groups according-to the codedesignation of said other'ofiices, control means common to said trunks, trunk testing means in said control means, means responsive to the registrationof the code designation of one of said oi'lices in said control means toconnect said trunk testing means with the trunks outgoing to said oflice, means under the control of said trunk testing means normally efiective toselect any idle one of said group of outgoing trunks to route a, call to said one Office, means to render a plurality of said outgoing trunks unavailable to said selecting l means-an operators position, and meansun'der the control of said operators position to render all of said trunks available tosaid'selecting'means.

trol means oversaid incoming trunks, means-responsive to the registration of thecodedesigna tion of one of said oflices in said control means to connectsaid control means with the trunks V outgoing to said office, means in said control means normally effective to select an idle one of said group of outgoing trunks to route a callto 1 said one office, means to render a number of saidoutgoing trunks unavailable to said control means, means under the control of said incoming trunk to vary the number of trunks made unavailable, an operators position, and means under the control of said operators position torender' all of said trunks available to said control means.

3. In a telephone'system, an automatic switching oflice, a'plurality of other oflices, said uto-1 matic switching oflice having "trunks of aplu-- rality of classes incoming from said other ofliccs and outgoing trunks to-said other offices arranged in groups according to thecode designations of said other oifices, control means common to said trunks, means for seizing said control means over one of said incoming trunks, means responsive to the registration of the'code designation of one of said oilices in said control means to connectsaid control means Withthe trunks outgoing to" said ofiice, means in said control means normally effective to select an idle one of said groupjof outgoing trunks to route a call to saidone'office, means to arbitrarily render a number of said outgoing trunks unavailable to said control means;

during times of heavy demand, means to vary the number of trunks made unavailable'in accordance with the class of saidincoming trunk'f an operators position and means under thefjcon trol of said operatorsposition to render all of v said trunks available to said control means,

4. In a telephone systemfan automatic switch{ ing oflice, a plurality of other oflices, said automatic switching ofiice having'trunks of a plurality of'classes incoming from said other oilices and outgoing trunks to, said otheroffices arrangedj in groups according to the code designations of said other ofiices, control means common to said, trunks, means for seizing said control means over,

one of said; incoming trunks, means responsive to the registration of k the v code designation, of one of said-offices in said control means to con.-

nect said control means with the trunks outgoing.

to said office, means in said "control means-snor mallyeffective to select an idle one of said group of outgoing trunks to route a call to said one office, a special operator, means ior arbitrarily reserving a numbenoi? saidtrunksior the exclumeans.

5. In a telephone, systemjan automatic switch? ing 'ofiice, a plurality of other oflices, said autos:v

matic switching, ofiice having 'trunks' of a plu rality of classes "incoming iromsaid other'oflices andoutg'oing trunks to said other oflices arranged:

in groups according ,tothe code designations: of

said other ofiices, control Emean eommon to said, trunks; means for seizingsaid control. meansowr;

L to the registration of the code designation of oneofsaidofifices in :said control means to connect said :control means with the trunks outgoing to said oiflca means in said control means normally effective to select an idle one of said group of outgoingtrunks to route a'call to said one ofiice, a special operator, means for arbitrarily reserving a number of said trunks for the exclusive use of said special operator during times of heavy de-- mand, imeanszunder thecontrol of said incoming trunk to render a variable number of the remaining trunks available tosaid control means, and;means effective i-fal-l ofsaid remaining trunks arebu y to cennect said incoming trunk with said special operators position. a

-6 In atelephone systemraii automatic switch. ing office, a plurality of other oflices, said auto-. matic switching officehaving incoming trunks from said other ofiices and'ou-tgoing trunks to said other oflices in groups according to the code designation of said other offices, control means position to render all of said testing relays eiiec tive.- v I V .7. In a telephone system, an automatic switchlng officaa plurality of other offices, said auto-V mane-switching oflice, having incoming trunks from said other .oiiices and outgoing-trunks to said other .ofiices in groups according to-the code designations of said other ofilces, control means common to said trunks, a plurality of test relays in said control means, means for seizing said control means over said incoming trunks, means responsive to the registration of the code designation of zone of said ofi'ices in said control means to connect said test relays with the trunks outgoing to said office, means under the control of said test relays normally effective to select an idle one of said group of outgoing trunks to route a call to said one ofiice, means to render a hum-,

ber of said testing relays inefiective, means under the control of said incoming trunk'to vary the number for testing relays made ineffective, an operator's position, andmeans under the control ofj'said ,operators position to render all of said testing relays efiective. 1

8. In a telephone system, an automatic switch-- ing ofiice, a plurality of other offices, said automatic switching oflicehaving trunks of a plurality of classes incoming from said other offices and outgoing trunks to said other ofiices in groups according to the code designations of said other ofllces, control means common to said trunks, a

, plurality of test relays in said control means,

' means for seizing said controlmeans over said incoming trunks, means responsive to the registration of the code designation of one of said oillces in said control means to connect said test relays with the trunks outgoing to saidtofiice,

means .under the control of said test relays nor-, 'mally effective to select an idle one of said group V of outgoing trunks-toroute a call to said one oflice, means to render a number of said testing relays ineffective, means to vary the number of automatic switching oihce having trunks from said other ofiices and outgoingtrunks to said other ofilcesin groups according to the testingrelays made .inefiect-ive in accordance the class of said incoming trunk and the=code designation registered, an zoperator s position, and means under the control of said operators position to render all of said testing relays effective.-

9. In a telephone system, an automatic switching ofiice, a plurality of other oflices, said automatic switching oflice having incoming trunks from said other oflices and outgoing trunks to said other offices in groups according to the code designations of said other ofilces, control means common to said trunks, means for seizing said control means over said incoming trunks, a frinrality of testing relays, means responsive to the registration of the code designation of one of said offices in said control means to connect said test-- ing relays with the trunks outgoing to said oiiice, a trunk selecting circuit, means in said [control means normally effective to place said selecting circuit under the control of a particular one of said test relays to select an idle one ofsaid group of outgoing-trunks to route 'a'call to said one oflice, -means to arbitrarily place said selecting circuit under the control of a different one of said testing relays to render a number of said outgoing trunks unavailable to said control means, means operated in accordance with the nature of said incoming trunk to determine the testing relay to which said selecting circuit is connected in order to vary the number of trunks made unavailable, an operators position, and means under the control of said operators position to render all of said trunks available to said control means. I v

10. In a telephone system, an automatic switching office, a plurality of other ofiices, Isa-id incoming code designations of said other oflices, control means. common to said trunks, means for seizing said control means over said incoming :t-runkaa plurality of testing relays, means responsive to the registration of the code designation of one'oi said oli'ices in said control means to connect said testing relays with the trunks outgoing to said ofiica'a trunk selecting circuit, means in said control means normally effective to place said selecting circuit under the control of a particular one of said relays to'select an idle one of -said group of outgoing trunks to route a call to said one office, means to arbitrarily place said selecting circuit under the control of a different one of said testing relays tore-rider a number of said outgoing trunks unavailable to said control means, means operated in accordance with the nature of said incoming trunk and the-code designation registered todetermine the testing relay to which said selecting circuit is connected in. order to vary thernumber of trunks made un- 7 available, an operators position, and means under the control of said operators position to render all of said trunks available to said control means. 7

- OSCAR MYERS.

' REFERENCES CITED The following references are of record in the file of this patent:

than. .28; 194i. 

